// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_
#define MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_

#include <list>
#include <memory>

#include "base/callback.h"
#include "base/macros.h"
#include "base/time/time.h"
#include "media/base/audio_decoder.h"
#include "media/base/demuxer_stream.h"
#include "media/base/media_log.h"
#include "media/base/sample_format.h"
#include "media/ffmpeg/ffmpeg_deleters.h"

struct AVCodecContext;
struct AVFrame;

namespace base {
class SingleThreadTaskRunner;
}

namespace media {

class AudioDiscardHelper;
class DecoderBuffer;

class MEDIA_EXPORT FFmpegAudioDecoder : public AudioDecoder {
public:
    FFmpegAudioDecoder(
        const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
        const scoped_refptr<MediaLog>& media_log);
    ~FFmpegAudioDecoder() override;

    // AudioDecoder implementation.
    std::string GetDisplayName() const override;
    void Initialize(const AudioDecoderConfig& config,
        CdmContext* cdm_context,
        const InitCB& init_cb,
        const OutputCB& output_cb) override;
    void Decode(const scoped_refptr<DecoderBuffer>& buffer,
        const DecodeCB& decode_cb) override;
    void Reset(const base::Closure& closure) override;

private:
    // There are four states the decoder can be in:
    //
    // - kUninitialized: The decoder is not initialized.
    // - kNormal: This is the normal state. The decoder is idle and ready to
    //            decode input buffers, or is decoding an input buffer.
    // - kDecodeFinished: EOS buffer received, codec flushed and decode finished.
    //                    No further Decode() call should be made.
    // - kError: Unexpected error happened.
    //
    // These are the possible state transitions.
    //
    // kUninitialized -> kNormal:
    //     The decoder is successfully initialized and is ready to decode buffers.
    // kNormal -> kDecodeFinished:
    //     When buffer->end_of_stream() is true and avcodec_decode_audio4()
    //     returns 0 data.
    // kNormal -> kError:
    //     A decoding error occurs and decoding needs to stop.
    // (any state) -> kNormal:
    //     Any time Reset() is called.
    enum DecoderState {
        kUninitialized,
        kNormal,
        kDecodeFinished,
        kError
    };

    // Reset decoder and call |reset_cb_|.
    void DoReset();

    // Handles decoding an unencrypted encoded buffer.
    void DecodeBuffer(const scoped_refptr<DecoderBuffer>& buffer,
        const DecodeCB& decode_cb);
    bool FFmpegDecode(const scoped_refptr<DecoderBuffer>& buffer,
        bool* has_produced_frame);

    // Handles (re-)initializing the decoder with a (new) config.
    // Returns true if initialization was successful.
    bool ConfigureDecoder();

    // Releases resources associated with |codec_context_| and |av_frame_|
    // and resets them to NULL.
    void ReleaseFFmpegResources();
    void ResetTimestampState();

    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;

    OutputCB output_cb_;

    DecoderState state_;

    // FFmpeg structures owned by this object.
    std::unique_ptr<AVCodecContext, ScopedPtrAVFreeContext> codec_context_;
    std::unique_ptr<AVFrame, ScopedPtrAVFreeFrame> av_frame_;

    AudioDecoderConfig config_;

    // AVSampleFormat initially requested; not Chrome's SampleFormat.
    int av_sample_format_;

    std::unique_ptr<AudioDiscardHelper> discard_helper_;

    scoped_refptr<MediaLog> media_log_;

    DISALLOW_IMPLICIT_CONSTRUCTORS(FFmpegAudioDecoder);
};

} // namespace media

#endif // MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_
